1. Field of the Invention
This invention relates to a data reproducing apparatus, and more particularly to an optical apparatus for reproducing data on an optical disk by using an optical head.
2. Description of the Related Art
An optical disk apparatus has an optical head (movable portion), which is moved in a radial direction of the optical disk to access a desired position thereon, and a data processing circuit (fixed portion) for performing various operations such as data reproduction based on the data read out from the optical disk. The movable and fixed portions are connected by means of flexible wires. Light reflected from the optical disk is subjected to photoelectric conversion by means of a plurality of photodetectors such as photodiodes arranged on the optical head and is converted into a plurality of electrical signals. The electrical signals are supplied to a current-voltage conversion circuit and an amplifier circuit provided in the fixed portion via the flexible wires. A focusing error signal and a tracking error signal are formed by processing a plurality of amplified signals. The focusing error signal is used to effect the focusing control for the objective lens, and the tracking error signal is used to effect the tracking control on the optical disk. Further, the plurality of signals are added together to form a reproduction signal (RF signal) of the recorded data.
The frequency bands of the focusing control signal and tracking control signal generally range from D.C. to 20 kHz, and the reproduction signal of the recorded data has a wide frequency band of D.C. to several MHz. For this reason, when the current-voltage conversion circuit for generating the sum signal to obtain a wide band reproduction signal is fixedly provided, the photodetector may be provided separately from the current-voltage conversion circuit, and therefore the reproducing operation may be influenced by induction noise or the like. U.S. Pat. No. 4,570,251 discloses such a disk apparatus.
When the above fact is taken into consideration, it seems desirable to set the current-voltage conversion circuit and the like on the optical head so as to bring the current-voltage conversion circuit as close as possible to the photodiode, thus minimizing the influence due to the induction noise. However, when the current-voltage conversion circuit and the like are mounted on the optical head, the weight of the optical head increases, lowering the access speed correspondingly.